1. Technical Field of the Invention
This invention relates to the epoxidation of propylene. More particularly, this invention relates to a process for the reaction of propylene with tertiary butyl hydroperoxide in solution in tertiary butyl alcohol in the presence of a peroxidation catalyst to provide propylene oxide and additional tertiary butyl alcohol.
Still more particularly, this invention relates to a process for preparing propylene oxide and tertiary butyl alcohol by reacting tertiary butyl hydroperoxide in solution in tertiary butyl alcohol with propylene in the presence of a soluble molybdenum catalyst, wherein the reaction is conducted in stages involving a reactor system comprising a first isothermal segment and a second adiabatic segment, wherein a feed mixture comprising a recycle stream, propylene, and a tertiary butyl alcohol solution of tertiary butyl hydroperoxide and a molybdenum catalyst are charged to the isothermal segment under reaction conditions sufficient to provide for a conversion of about 60 to 80 wt. % of the tertiary butyl hydroperoxide to thereby provide an intermediate reaction mixture, wherein a recycle stream constituting about 25 to about 100 wt. % of the combined weight of the propylene and tertiary butyl alcohol solution is removed as the recycle stream and wherein the remainder of the intermediate reaction product is charged to the adiabatic segment for the conversion of an additional 20 to 40 wt. % of the tertiary butyl hydroperoxide to reaction products.
2. Prior Art
The reaction of an olefin such as propylene with a hydroperoxide such as tertiary butyl hydroperoxide in solution in a solvent such as tertiary butyl alcohol in the presence of a soluble molybdenum catalyst is disclosed in Kollar U.S. Pat. No. 3,351,635. Kollar teaches that in general, from about 0.5 to 100 moles of olefin may be used per mole of hydroperoxide, the preferred molar ratio being within the range of about 2 to about 10 moles of olefin per mole of hydroperoxide.
Marquis et al. in U.S. Pat. No. 4,891,437 disclose an improvement on the Kollar process in the reaction of propylene with tertiary butyl hydroperoxide is concerned wherein the reaction is conducted in a medium composed of 60 wt. % or more of polar components which is formed by utilizing a molar ratio of propylene to tertiary butyl hydroperoxide of about 0.5 to 2 moles of charged propylene per mole of charged hydroperoxide, the reaction being conducted in solution in tertiary butyl alcohol in the presence of a molybdenum catalyst. Variations in the Marquis et al. process and in the preparation of catalysts useful therefore are disclosed in Marquis et al. U.S. Pat. No. 4,845,251 and U.S. Pat. No. 5,107,067.
British Patent No. 1,298,253 discloses a process for the staged reaction of propylene with tertiary butyl hydroperoxide in the presence of tertiary butyl alcohol and a soluble molybdenum catalyst wherein the reaction product from the first stage is fractionated to provide a lighter fraction lo which is recycled to the beginning of the first stage and a heavier fraction which is charged to the second stage of the epoxidation process.
Marquis et al. U.S. Pat. No. 4,992,566 and Marquis et al. U.S. Pat. No. 5,093,506 disclose single stage processes for the reaction of propylene with tertiary butyl hydroperoxide wherein the reaction product is fractionated to provide a propylene stream for recycle.
Russell U.S. Pat. No. 3,418,340 discloses a process for the production of propylene oxide by the reaction of propylene with tertiary butyl hydroperoxide involving a recycle of the propylene wherein the propylene is further fractionated to remove oxygen prior to recycle.
Stein et al. U.S. Pat. No. 3,849,451 discloses a process wherein propylene is reacted with tertiary butyl hydroperoxide in solution in tertiary butyl alcohol in a single stage compartmented reactor operated under conditions such that propylene and propylene oxide are vaporized during the course of the reaction and wherein the vapors are recovered and distilled to provide a propylene fraction for recycle.
D'Aubigne et al. U.S. Pat. No. 4,002,687 discloses a process for the hydroperoxidation of a hydrocarbon such as isopentane or isobutane with oxygen using a plurality of stages with water washing between stages.